There are known in the art a great variety of devices for providing information to an operator, such as the pilot of an airplance. These devices include visual displays, such as lighted control panels, heads-up displays, cathode ray tubes and the like, and audio displays, such as buzzers, horns, simulated speech and similar devices.
There exist operational environments wherein the amount of information which it is sought to provide to the operator exceeds that which can efficiently be received through visual and auditory senses. Such environments will be termed "information saturated" environments. An example of an information saturated environment is the cockpit of a modern high performance fighter aircraft. Overloading a given sense with information in an informations aturated environment may cause a decrease in performance.
There exist environments wherein an operator is required to respond immediately to information inputs which are spatially related to his position. The use of existing two-dimensional displays requires the operator mentally to transform the displayed information into his own three dimensional positional framework. Such a transformation requires concentration and takes time, and is therefore undesirable in an environment wherein extreme speed and accuracy of operator response are essential.